This invention is an improvement over the sustained-release oral drug dosage forms described in U.S. Pat. Nos. 5,007,790 and copending U.S. Ser. No. 08/453,144 which was filed May 30, 1995. The dosage forms described therein consist of a plurality of solid particles composed of a solid drug dispersed in either a crosslinked or non-crosslinked, hydrophilic, water-swellable polymer. In these dosage forms, the polymers in which the drug is dispersed imbibe water, causing the particles to swell which promotes their retention and also allows the drug contained in the particles to dissolve and diffuse from the particles. Over a period of many hours, the drug diffuses from the particles at a rate related to the dissolution rate of the drug. However, only after the drug has substantially dissipated from the dosage form, does the polymer dissolve.
Poly(ethylene oxide) and hydroxypropyl methylcellulose polymers have been used in the pharmaceutical industry for controlled drug delivery systems including, for example, oral drug delivery systems. However, such polymers have not previously been used in gastric retentive, oral drug delivery systems.